<s>
Carrierless	B-Device
amplitude	I-Device
phase	I-Device
modulation	I-Device
(	O
CAP	O
)	O
is	O
a	O
variant	O
of	O
quadrature	B-Device
amplitude	I-Device
modulation	I-Device
(	O
QAM	B-Device
)	O
.	O
</s>
<s>
Instead	O
of	O
modulating	O
the	O
amplitude	O
of	O
two	O
carrier	O
waves	O
,	O
CAP	O
generates	O
a	O
QAM	B-Device
signal	O
by	O
combining	O
two	O
PAM	B-Device
signals	O
filtered	O
through	O
two	O
filters	O
designed	O
so	O
that	O
their	O
impulse	O
responses	O
form	O
a	O
Hilbert	B-Algorithm
pair	I-Algorithm
.	O
</s>
<s>
If	O
the	O
impulse	O
responses	O
of	O
the	O
two	O
filters	O
are	O
chosen	O
as	O
sine	O
and	O
a	O
cosine	O
,	O
the	O
only	O
mathematical	O
difference	O
between	O
QAM	B-Device
and	O
CAP	O
waveforms	O
is	O
that	O
the	O
phase	O
of	O
the	O
carrier	O
is	O
reset	O
at	O
the	O
beginning	O
of	O
each	O
symbol	O
.	O
</s>
<s>
If	O
the	O
carrier	O
frequency	O
and	O
symbol	O
rates	O
are	O
similar	O
,	O
the	O
main	O
advantage	O
of	O
CAP	O
over	O
QAM	B-Device
is	O
simpler	O
implementation	O
.	O
</s>
<s>
For	O
HDSL	O
,	O
the	O
American	O
ANSI	O
standard	O
specifies	O
2B1Q	B-Protocol
rather	O
than	O
CAP	O
,	O
while	O
the	O
European	O
ETSI	O
ETR	O
152	O
and	O
the	O
international	O
ITU-T	O
G.991.2	O
standards	O
specify	O
both	O
CAP	O
and	O
2B1Q	B-Protocol
.	O
</s>
<s>
The	O
standardized	O
variants	O
of	O
ADSL	O
,	O
ANSI	O
T1.413	O
Issue	O
2	O
and	O
G.dmt	O
,	O
as	O
well	O
as	O
the	O
successors	O
ADSL2	O
,	O
ADSL2+	O
,	O
VDSL2	O
,	O
and	O
G.fast	O
,	O
do	O
not	O
specify	O
CAP	O
,	O
but	O
rather	O
discrete	B-Protocol
multi-tone	I-Protocol
(	O
DMT	O
)	O
modulation	O
.	O
</s>
<s>
The	O
range	O
of	O
25kHz	O
to	O
160kHz	O
is	O
allocated	O
for	O
upstream	B-Application
data	O
traffic	O
and	O
the	O
range	O
of	O
240kHz	O
to	O
1.5MHz	O
is	O
allocated	O
for	O
downstream	O
data	O
traffic	O
,	O
in	O
a	O
frequency-division	O
duplexing	O
(	O
FDD	O
)	O
scheme	O
.	O
</s>
